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Cogeneration is nothing new to the clean-water industry, but in southern California, the Orange County Sanitation District has taken it one step farther, hosting a trigeneration demonstration project: a facility that turns biogas it into hydrogen, electricity and heat.

With the cooperation of the National Fuel Cell Research Center at the University of California Irvine, the $8 million research project at the 103 mgd Fountain Valley Wastewater Treatment Plant began in September 2010, testing the use of a fuel cell to tap the energy potential of biogas.

The National Fuel Cell Research Center collaborated with technology developers Air Products and FuelCell Energy to design a fuel cell demonstration project. Then they contacted the Orange County district about hosting it. The project is funded by grants from the California Air Resources Board, the U.S. Department of Energy, the South Coast Air Quality Management District, and Southern California Gas Company.

Key to the system is a 300 kW fuel cell that performs the direct fuel-to-energy conversion through an electrochemical process instead of combustion. The project is the first in the world to use digester gas for a fuel cell, which generates the hydrogen for automotive fuel, electricity for the clean-water plant, and heat that could be used for purposes such as heating the anaerobic digesters that produce the biogas.

Supporting the cause

“We were interested from a couple of perspectives,” says Ed Torres, director of operations and maintenance for the Orange County Sanitation District. “We were looking at new ways to bring power into our facility because our demand was increasing and the percentage of power we generate on site was starting to diminish. The South Coast Air Basin is the most heavily regulated air district in the nation, so we were also interested in the ability to meet possible future mandates to move to alternative energy.”

The district also wanted to support the state’s efforts to expand use of and infrastructure for hydrogen-fueled vehicles and a project called the California Hydrogen Highway. The state wants to have 100 hydrogen fueling stations by 2017; it now has 13 research stations and nine public fueling stations.

The wastewater plant’s hydrogen fueling station is one of four in Orange County and the only one that makes hydrogen for dispensing — the others receive hydrogen produced from natural gas. The Orange County station is located next to the plant’s natural gas fueling station, which has been available to the public for years.

Substantial production

“There is hydrogen generated in the fuel cell itself, and it gets pumped over to storage at the fueling station in front of our plant,” says Torres. Air Products, a provider of hydrogen fueling technology, installed the fuel station and owns and maintains it.

From its inception in September 2010 through September 30, 2013, the Orange County facility had processed 16.8 million cubic feet of digester gas to make more than 36,000 pounds of hydrogen and 2.4 million kWh of electricity.

Waste heat is not being used as part of the demonstration project. “It’s quite a distance from the fuel cell to the waste heat line we use to heat our digesters,” says Torres. “It wasn’t cost-effective for a small demonstration project. On any kind of large-scale project, it would be utilized.”

One thing the project has shown is improved treatment of the biogas for use in the fuel cell. “Others have struggled in the past in trying to clean the biogas and maintain the pretreatment system,” notes Torres. “This one uses a fairly new pretreatment system from Quadrogen of Canada. It’s essentially removing all of the sulfides and siloxanes.”

Fleet additions

For now, the hydrogen fuel is used by the sanitation district, which is leasing one Toyota FCHV hydrogen test car and fuel cell vehicles from four other automakers. The district’s $300 monthly vehicle lease payment includes all the fuel it consumes.

The district has not decided whether to expand its fleet of hydrogen vehicles. “We like the fuel,” says Nick J. Arhontes, director of facilities support services. The hydrogen is used by a fuel cell in the vehicle to generate electricity to power an electric motor. The only tailpipe emissions are water vapor.

“As a fleet manager, we’ll have to look at the availability of fuel in the future and at cost-effectiveness,” says Arhontes. “Whether we keep the demonstration project and actually lease or purchase some of these vehicles is unknown at this time.” The project team is working on a strategy to continue the demonstration project.

The district has renewed its annual lease on the FCHV prototype passenger vehicle, which is similar to a Toyota Highlander sport utility vehicle. “We’ve been very happy with it, but could get into another product,” says Arhontes. “I do know a lot of manufacturers are looking at launching hydrogen vehicles in about the 2015 timeframe.”

In the meantime, the district will continue to use compressed natural gas as its primary alternative vehicle fuel. “This could be another area in which we end up growing our alternative-fuel fleet,” says Arhontes. “We could also see hydrogen used for small vehicles in the plant where we use a lot of electric carts for carrying cargo and personnel. We’ll have to wait to see what the market brings us.”

Immature technology

The largest question is still the economics. Torres notes that fuel cell technology remains expensive at $3,000 to $4,000 per kilowatt installed cost versus about $1,000 per kilowatt for a typical internal combustion engine. “So it’s still not competitive, and there is still uncertainty about the life of the fuel cell stack,” Torres says. Such issues are one reason for conducting demonstration projects and a reason states and the federal government are funding the research and trying to build up the hydrogen infrastructure.

Torres calls it a chicken-or-egg situation: There aren’t many hydrogen cars on the road, but there aren’t a lot of fueling stations to support them as the number grows. “Do you build the infrastructure and wait for the car manufacturers to build up to it?” Torres asks. “If you put it at a plant like ours, if you don’t have the utilization by vehicles, you just produce electricity and power your plant as the demand for vehicle fuel grows. So it can be a viable investment strategy because we can utilize the hydrogen in other ways.”

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